烟气中H2S和SO2的检测

从采样、测量原理、仪表结构等几个方面介绍了利用紫外光谱吸收原理的多种气体分析仪,并对该分析仪在SRU装置的烟气中H2S和SO2的检测进行了介绍,经实践证明,该分析仪的应用效果良好.     

苯乙烯装置氢气压缩机凝液排放改造

苯乙烯装置氢气压缩机冷却分离器产生的凝液中含有部分物料,且排液时易夹带氢气,直接去生产废水处理系统,浪费物料,造成污水处理费用增加,且存在安全隐患和环境污染。为了解决这些问题,增加氢气压缩机到油水分离器的排液管线,达到节能减排、消除环境污染和安全隐患的目的。     

基于模型的H263＋可扩展性编码

提出了基于模型的视频时空可扩展性编码方法，即根据人眼视觉敏感程度的不同，将视频中的每帧图象根据模型划分为程度不同的区域，对每一个区域分配不同的时间和空间分辨率，以期在极低码率的传送环境中保证人眼敏感区域的图象质量和传送效率。     

网络新技术——IP电话及发展

本文介绍了IP网络技术及应用、IP电话的概念、IP电话发展状况、IP电话标准协议及标准机构、IP电话与传统电话相比的优势与不足 ,并简单论述了作者对IP电话发展的意见。     

NMR study of the role of isopropylsulfates in the two-step “conjunct oligomerization” of propylene and isopentane–propylene alkylation catalyzed by 95% sulfuric acid

“Conjunct oligomerization” of propylene or the isopentane–propylene alkylation catalyzed by an excess of 95% sulfuric acid was performed in two consecutive steps. First di-isopropylsulfate was prepared by interaction of sulfuric acid with propylene. The ester was then either decomposed at room temperature in the presence of the 5–10 molar excess of 95% acid or was used in the acid-catalyzed alkylation of isopentane. In situ ¹H and ¹³C NMR study of the reaction mixture of “conjunct oligomerization” indicated that the diester participates in two equilibria with sulfuric acid. The first one transforms the diester into a monoester. The second equilibrium corresponds to protonation of the monoester with an excess of sulfuric acid. This converts a minor fraction of the mono-alkylsulfate into isopropyl carbenium ions that are only weakly solvated with sulfuric acid: C₃H₇HSO₄ + H₂SO₄ ⇄ C₃H₇ ⁺ H₂SO₄ + HSO₄ ⁻. The subsequent reactions of alkyl carbenium ions with the non-protonated alkylsulfate result in final products of “conjunct oligomerization” while in the presence in the reaction mixture of isopentane, alkylation with the predominant formation of C₈ branched paraffins takes place. A very low yield of propane indicates a minor role of hydride transfer in alkylation. Another unexpected result is the absence in both reaction mixtures of propylene. These findings are in contradiction with the classical mechanism of isoparaffin–olefin alkylation by Schmerling. Therefore, an alternative mechanism of this reaction is suggested via a direct alkylation of isopentane with the mono-alkylsulfate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Bernard H. Fox (1917-2001).

Memorializes B. H. Fox, a research scientist internationally known for his work on the epidemiology and etiology of cancer. Fox was instrumental in establishing a new field of research best described as biopsychosocial cancer epidemiology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Do vertical tax externalities lead to tax rates being too high? A note

When both vertical and horizontal externalities are at work in a federation, they generally distort levels of taxation in opposite directions. This article is an extension of the Keen and Kotsogiannis (Am Econ Rev March: 363–370, 2002) model. It focuses on state tax policy when states provide an industrial public good increasing firms’ marginal productivity rather than a residential public good intended to households. We find that some results related to whether equilibrium state taxes are likely to be too high or too low are much more complex when state-provided industrial public goods are considered. First, we show that in the presence of industrial public goods, a dominant vertical externality may result in state tax rates being too low (and not too high as it is the case with residential public goods). Second, we find that under certain conditions, horizontal and vertical externalities may point in the same direction and reinforce each other towards tax rates being too high or too low.     

Modelling of equilibrium solubility of CO2 and H2S in aqueous diglycolamine (DGA) solutions

Information on acid gas solubility in solvents utilized is needed for the design of gas plants. A mathematical model for the prediction of equilibrium solubility of CO₂ and H₂S in aqueous 2-amino-2-(ethoxy)ethanol (DGA) solutions is presented. The equilibrium constants, K₁ and K₂, representing a simple proton transfer reaction and the carbamate formation reaction, respectively, were found to be functions of temperature and free acid gas concentration. In addition, K₂, was affected by DGA concentration as well. Model predictions agree favourably with experimental data.     

Swelling behaviour of rubber vulcanizates: 2. Effects of tensile strain on swelling

The effects of tensile strain on the swelling behaviour of acrylonitrile-butadiene copolymer rubber vulcanizates were studied by real-time pulsed nuclear magnetic resonance (n.m.r.) measurements and volume swelling measurements at equilibrium. It was shown that tensile strain causes an increase of the initial swelling rate evaluated by n.m.r. measurements and of the swelling ratio of the rubber matrix at equilibrium. This behaviour was discussed qualitatively in terms of the molecular mobility of the network chains on the basis of Treloar's theory for swelling under deformation. It was suggested that the presence of reinforcing fillers in the rubber matrix exerts two noticeable effects on swelling under deformation: (1) a transient effect through some oriented structure induced by stretching, which restricts the increase of the swelling rate; (2) a strain amplification effect, which causes the increase of the average local strain in the rubber matrix and enhances the swelling ratio more remarkably proportional to the filler concentration as compared with that of the unfilled system.     

Essential elements and contaminants in edible tissues of European and American lobsters

In several European countries clawed lobsters, such as the European (Homarus gammarus) and American (H. americanus) ones are widely consumed. Yet, information about essential elements and contaminants in both species is still scarce. Therefore, the aim of this work was to characterise the elemental content in the edible part (muscle, hepatopancreas, gonads and roe) of both homarids and to compare them with the daily intake recommendations and maximum allowed levels. Two techniques were employed: energy-dispersive X-ray fluorescence (EDXRF) to quantify Cl, S, K, Ca, Fe, Cu, Zn, As, Se, Br and Sr; and flame atomic-absorption spectrometry (FAAS) to analyse Na, Mg, Mn, Cd, Hg and Pb. Significant differences were found in the elemental composition of edible tissues of both species, likely reflecting the distinct physiological role of those tissues: muscle (higher: Na, Mg, Ca and Sr; lower: Fe, Se, Cd); hepatopancreas (higher: Fe, Cu, Br and Cd); gonads (lower: Cl, Ca, Zn and Hg); and roe (higher: Na and Br; lower: K and As). Statistical differences in the elemental composition of each tissue were found between both homarids: Muscle (Na, Se, As and Hg); Hepatopancreas (Na, Mg, Fe, Cu, Se, Br and Hg); and gonads (S and Zn). Since the geographical distribution of both species is different, the differences likely reflect distinct elemental composition in the aquatic environment and, consequently in the feed chain. Both lobster species were rich sources of Na, Cl, Cu, Zn and Se for human consumption. Regarding contaminants, only Cd was detected at high concentrations in the hepatopancreas of both homarids. Despite Cd values were well above the maximum allowed level set by the European Commission for crustaceans’ muscle, so far any limit value was set for crustaceans’ hepatopancreas. Nonetheless, the present study recommends avoiding or moderately consuming this tissue in homarids.